The present invention relates to a method of manufacturing a fuel inlet for filling fuel, such as gasoline, into a fuel tank of an automobile or the like.
Conventionally known as a fuel inlet for filling fuel, such as gasoline, into a fuel tank of an automobile or the like is, for example, a fuel inlet, as shown in FIG. 4, comprising an inlet pipe 102 for conveying fuel into the fuel tank, a filling part 104 formed by expanding an end of the inlet pipe 102, the filling part 104 being provided with a helical groove 104b for engagement with a cap (not shown), and a breather tube 110 for venting air from the fuel tank when the fuel tank is filled with fuel, the breather tube 110 opening into the inlet pipe 102 in the vicinity of the end thereof.
In the case of such a fuel inlet, for the purpose of rust proofing, galvanized steel pipes are used for the inlet pipe 102 and the breather tube 110, and furthermore, any coating is applied thereto.
In recent years, however, the influence of materials used in automobiles upon the global environment has become a major concern for more and more people, and regulations on use of such materials have been made tighter. Also, a further improvement of components of a fuel system is desired in view of their durability. Furthermore, a further improvement is also required in view of their anti-rust property.
The present invention was made to meet the aforementioned requirements. More particularly, the object of the invention is to provide a method of manufacturing a fuel inlet having an improved anti-rust property.
In order to attain this object, there is provided a method of manufacturing a fuel inlet, the fuel inlet comprising an inlet pipe for conveying fuel into a fuel tank and a breather tube for venting air from the fuel tank toward an end of the inlet pipe when the fuel is filled into the fuel tank, the method comprising:
a preparatory process in which stainless pipes for manufacturing the inlet pipe and the breather tube are prepared, a pipe expanding process in which an end portion of the inlet pipe is enlarged in diameter to form a filling part, a screw-thread forming process in which a helical groove is formed on a periphery of the filling part, a welding process in which the breather tube is welded to the inlet pipe, and a coating process in which a cationic electrodeposition coating is applied to the fuel inlet.
As material for the stainless pipes, SUS436 is preferably used. Also, in the welding process, an open end of the breather tube may be joined to a periphery of the inlet pipe by means of projection welding. Furthermore, in the screw-thread forming process, a core bar on which a groove is formed is inserted into the filling part, and a roller is moved along the groove, while being pressed against the periphery of the filling part, thereby forming the helical groove.